NATURE OF THE BULK DEFECTS IN GAAS THROUGH HIGH-TEMPERATURE QUENCHINGSTUDIES

Deep-level transient spectroscopy has been applied to n-type horizonta l gradient freeze grown GaAs that has been subjected to thermal stress ing (quenching) and varying degrees of arsenic outdiffusion during rap id thermal annealing. The concentrations and activation energies of th e various deep donor levels have been monitored. As a result of the ex ternal excitations in the lattice due to the thermal stress (quenching ), dramatic effects occur in the defect level structure that could be of importance to device technology. It is found that the native ELS gr oup of defects is nearly absent in rapid thermally annealed material, while the levels EL5 and EL8 appear with EL3 becoming a dominant level that could act as a recombination center. With the lengthening of ann ealing time and significant As outdiffusion, there is a general reduct ion of the EL2, EL3, and EL5 defect concentrations together with a com plete removal of EL8. Moreover, the EL2 activation energy may be varie d from 0.827 to 0.922 eV by controlling the level of As out-diffusion. These observations are discussed in terms of the As-Ga-As-i model of the EL2 defect and the V-As-V-Ga divacancy model for the EL6 group of defects. The EL3, EL5, EL8, and EL15 defect levels seen in samples sub jected to rapid thermally quenching are attributed to the breakup of V -As-As-i Frenkel pair defects known to be present in the as-grown mate rial.